Cambridge A Level Physics 9702 — 2009 Oct/Nov Paper 3 · Variant 1

This document consists of 9 printed pages and 3 blank pages. DC SJF5064/CG 11638/4 © UCLES 2009 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer both questions. You will be allowed to work with the apparatus for a maximum of one hour for each question. You are expected to record all your observations as soon as these observations are made, and to plan the presentation of the records so that it is not necessary to make a fair copy of them. The working of the answers is to be handed in. Additional answer paper and graph paper should be submitted only if it becomes necessary to do so. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. All questions in this paper carry equal marks. * 3 3 7 6 0 4 0 6 4 0 * PHYSICS 9702/31 Paper 31 Advanced Practical Skills 1 October/November 2009 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

3 9702/31/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use You may not need to use all of the materials provided. 1 In this experiment you will investigate the position of a wooden rod suspended in water as the depth of the water is varied. Assemble the apparatus, as shown in Fig. 1.1, then add water to the beaker until the mass attached to the bottom of the rod is completely covered and is not touching the bottom of the beaker. h z mass beaker wooden rod set of springs stand clamp Fig. 1.1 (a) Record h and z, as shown in Fig. 1.1. h = ………………………………… cm z = ………………………………… cm

4 9702/31/O/N/09 © UCLES 2009 For Examiner’s Use (b) Add more water to the beaker and repeat (a). Repeat this procedure until you have six sets of readings for h and z. (c) (i) Plot a graph of z on the y-axis against h on the x-axis. Draw the line of best fit. (ii) Determine the gradient of the line. gradient = …………………………………

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6 9702/31/O/N/09 © UCLES 2009 For Examiner’s Use (d) (i) Use the vernier calipers to determine the diameter d of the wooden part of the rod. d = ………………………………… (ii) Calculate the cross-sectional area A of the wooden part of the rod, using the relationship A = πd 2 4 . A = ………………………………… m2 (e) The relationship between z and h is k ρAg z = c + h + 1 ⎛ ⎞ ⎝ ⎠ where c is a constant, k is the spring constant, ρ is the density of water (1000 kg m–3), and g is the acceleration of free fall (9.81 m s–2). Using your answers from (c)(ii) and (d)(ii), determine the value of k. Give an appropriate unit. k =…………………………………

7 9702/31/O/N/09 [Turn over BLANK PAGE Please turn over for Question 2.

8 9702/31/O/N/09 © UCLES 2009 For Examiner’s Use You may not need to use all of the materials provided. 2 In this experiment you are provided with a ball suspended by a thread. You will investigate how the recoil distance is related to the length of the thread when the ball is struck by a moving marble. (a) Assemble the apparatus, as shown in Fig. 2.1, with the thread clamped between the two wooden blocks so that l is about 50 cm. l wooden blocks Fig. 2.1 Measure l. l = …………………………………

9 9702/31/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use (b) Further assemble the apparatus, as shown in Fig. 2.2. When the marble is released from rest, it rolls down the tube and hits the centre of the ball. Adjust the tilt of the tube so that the recoil distance d of the ball is about 20 cm. d wooden blocks tube marble (before release) plastic beaker to catch marble Fig. 2.2 (i) Measure d. d = ………………………………… (ii) Explain how you used the apparatus to ensure that d was measured as accurately as possible. … … … … …

10 9702/31/O/N/09 © UCLES 2009 For Examiner’s Use (iii) Estimate the percentage uncertainty in d. percentage uncertainty in d = ………………………………… (c) If air resistance is ignored, theory predicts that k = l – l 2 – d 2 where k is a constant. (i) Calculate a value for k. k = ………………………………… (ii) Justify the number of significant figures you have given for your value of k. … … … (d) Without changing the position of the tube, shorten the thread to give a different value of l. Lower the clamp holding the thread to reposition the ball at the end of the tube, and then determine values of l, d and k for the new arrangement. l = ………………………………… d = ………………………………… k = …………………………………

11 9702/31/O/N/09 © UCLES 2009 For Examiner’s Use (e) By explaining whether your results indicate that k is constant, show whether the relationship in (c) is supported. … … … … (f) (i) State four sources of error or limitations of the procedure in this experiment. 1. … … 2. … … 3. … … 4. … … (ii) Suggest four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures. 1. … … 2. … … 3. … … 4. … …

12 9702/31/O/N/09 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2009 question paper for the guidance of teachers 9702 PHYSICS 9702/31 Paper 31 (Advanced Practical Skills 1), maximum raw mark 40 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes must be read in conjunction with the question papers and the report on the examination. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2009 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 31 © UCLES 2009 1 (a) First values for h and z, to the nearest mm. [1] (b) Measurements – Add up the number of sets of values of z and h and put a ringed total [4] by the table. Four marks for six sets of readings of z and h, three for five sets, etc. (–1 if help given by supervisor, -1 if wrong trend i.e. h↑ z↓) Maximum value for z - h greater than 6.0 cm [1] Column headings [1] Each column heading must contain a quantity and a unit where appropriate. Ignore units in the body of the table. There must be some distinguishing mark between the quantity and the unit (i.e. solidus is expected, but accept, for example, h (mm)). Consistency of presentation of raw readings [1] All raw values of h and z must be given to the same number of decimal places. (c) (i) (Graph) Axes [1] Sensible scales must be used. Awkward scales (e.g. 3:10) are not allowed. Scale markings should be no more than 3 large squares apart. Scales must be chosen so that the plotted points occupy at least half the graph grid in both x and y directions. Scales must be labelled with the quantity being plotted. Ignore units. Allow reversed axes but do not allow the wrong graph. (Graph) Plotting All observations must be plotted. Put a ringed total of plotted points. [1] Ring and check a suspect plot. Tick if correct. Re-plot if incorrect. Work to an accuracy of half a small square. Penalise ‘blobs’ – dia. of plots must be < ½ a small square. (Graph) Line of best fit [1] Judge by scatter of at least 5 trend points about the candidate's line. There must be a fair scatter of points either side of the line. Indicate best line if candidate's line is not the best line. (Graph) Quality of results Judge by scatter of points about the best fit line. [1] All points in the table (of which there must be at least 5) must be within + 0.3 cm (to scale) on the h axis. (ii) Gradient The hypotenuse must be at least half the length of the drawn line. [1] Read-offs must be accurate to half a small square. If incorrect write in the correct [1] value. Check for ∆y/∆x (i.e. do not allow ∆x/∆y).

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 31 © UCLES 2009 (d) (i) Raw value(s) for d to nearest 0.1 mm or 0.01 mm [1] 18.00 mm < d < 27.00 mm. Unit required. Repeated readings for d. [1] (ii) A calculated correctly. Allow ecf. Check value. If incorrect, write in the correct value. [1] Significant figures for A must be the same as, or one more than, the sig. figs. of the [1] raw values of d. (e) Method – value from (c) (ii) equated to k/ρAg + 1 [1] Substitution methods lose both (e) marks Calculation - value for k in range 4 to 6 Nm-1.(allow 3.50 < k < 6.49). [1] (or refer to supervisor’s value). Unit required. Ignore SF. This mark is conditional on achieving the previous mark. [Total: 20]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 31 © UCLES 2009 2 (a) (i) First value of l, with unit, to nearest mm. (40 ≤ l ≤ 60 cm) [1] (-1 if help given by supervisor) (b) (i) First value of d ( 18 cm < d < 22 cm) with consistent unit. [1] (ii) Method of measuring d accurately – two details of procedure e.g: [2] • Method of consistent release of marble • Use of named item(s) as marker(s) • Refining position of marker • Place ruler underneath and view vertically from above. Do not allow ‘repeats’ (iii) Percentage uncertainty in d. [1] Range of absolute uncertainty: 2 mm < ∆d < 10 mm. If repeated readings have been done then the uncertainty can be half the range. Correct ratio idea required. x 100% implied. (c) (i) First value of k, substitution correct. Consistent unit. [1] (ii) Justification for s.f. in value of k. [1] Either: k must be given to same no. of SF, or one more than, l and d. Or: k must be given to same no. of SF, or one more than, l or d, whichever has the least no. of SF. (d) Second values of l and d. [1] Evidence of repeat readings for first or second value of d. [1] Second d less than first d. [1] (e) Percentage difference (or fractional difference) in k values calculated. [1] Sensible conclusion consistent with uncertainty of 20% [1] in values of k, or candidate’s stated uncertainty.

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 31 © UCLES 2009 (f) Identifying limitations and suggesting improvements: (f) (i) Limitations/ sources of error (max 4 marks) (f) (ii) Improvements (max 4 marks)) Ignore: A Only two readings/two readings are not enough (to draw a valid conclusion) Take more readings and plot a graph/calculate more k values repeat readings B Hard to measure d because ball moves too quickly/ too fast/only stationary for short time … Use video and play back slowly/ frame by frame Use slow motion camera Use position sensor/motion sensor Allow light gates, adjusting position until beam interrupted Use a high-speed camera/computer/data logger C Difficulty in releasing marble consistently/ from rest/without applying a force Description of a mechanism to release marble e.g. slot in tube + card Change angle D Parallax error in measurement of d Description of method of reducing parallax error requiring additional equipment e.g. shadow projection view at eye level view from above use a marker E Incorrect alignment/ inconsistent collisions/ different paths down tube Use narrower tube F Motion of ball affected by air movement/ ball swings around Turn off fans/air con. Shield from draughts Use a closed room/vacuum refs to air resistance heavier ball G Difficult to measure l because it is hard to judge the position of the centre of the ball Measure diameter of ball using vernier calipers Measure l to top and bottom of ball and average. [Total:20]